1. Field of the Invention
The present invention relates to a device and a method for holding and guiding elongated objects, for example, multiple wire bundles, multiple sheathed wires, multiple flat ribbon or flat cable bundles. In particular, the present invention relates to a device and method for holding and guiding wire bundles that are used in automobiles.
2. Background of the Invention
Wire bundles, or wire harnesses, are used in automobiles to form electrical connections between a battery and various electric components. Frequently, such harnesses have been used to connect parts located in the engine compartment of a motor vehicle with parts that are located in a passenger compartment of the motor vehicle. In order for the harnesses to extend between the engine compartment and the passenger compartment, the harnesses typically pass through a perforation formed in a partition between the engine compartment and the passenger compartment. Standardly, the engine compartment of a motor vehicle is open to the road surface and, therefore, moisture from the road surface may reach the outer surfaces of the wire harness or the individual wires forming the wire harness. This moisture, for example, drops of water, tends to migrate on insulated surfaces of the individual wire or on the surface of the entire wire harness. If the water droplets migrate to a portion on the wires that is not insulated, typically the ends of the wires, there is a likelihood that the vehicle""s electric system will be compromised.
A device for holding and guiding elongated objects, such as multiple wire bundles, is disclosed in DE 196 40 816 A1. The DE 196 40 816 A1 device is divided along a center plane and comprises two arcuate press elements, which during use, are brought into engagement in ring-like fashion around the elongated object, e.g., wire bundle or the like. With the aid of suitable fastening devices, the two arcuate press elements may be interconnected and apply the desired contact pressure to the elongated object, which is surrounded by the elements.
Because this known device from DE 196 40 816 A1 is bipartite, wire bundles or multiple wire bundles may be produced in an automatic manner. In the initial industrial production of multiple wire bundles, e.g., when cable harnesses were first introduced in automobile applications, wire bundles were made by hand on so-called shaping boards. The individual wires of a multiple wire bundle needed to be hand threaded through annularly closed or ring like structures, such as rubber sleeves or boots, heat-shrinkable tubes, insulating tubes, or the like. The DE 196 40 816 A1 device obviates the need for hand-threading.
DE 196 40 816 A1 also discloses sheathing the outer circumferences of each of the two parts of the dividable devices with a soft rubber sleeve, so that the device may be used as a wall passage, with the outer edge of the rubber sleeve being brought into sealing engagement with the inner circumference of an opening extending through the wall. The parting surfaces of the rubber sleeve are not as dimensionally stable as opposed to material-saving types, with the effect being that upon the introduction of outer forces, a local opening is likely to be presented in the area of the parting surfaces. In turn, this local opening jeopardizes the required fluid tightness in the area of the parting surfaces.
DE 196 40 816 A1 further teaches that the passage of liquids and gases through the wire spaces or gores is effectively prevented in the area of the bipartite device with the help of butyl. For the purpose of simplicity, this phenomenon, referred to as xe2x80x9cwater tightness in the longitudinal directionxe2x80x9d, and occurs because the individual wires are glued in parallel with one another onto a butyl layer of an adhesive tape. In addition, the individual wires connected to the adhesive type are arranged layerwise in a part of the divided device, so that the individual wires are sandwiched between butyl layers. The passage opening, which is formed between the two arcuate press elements, is undersized with respect to the wire system provided with the butyl adhesive. Therefore, a uniform pressure is exerted on the wire bundles when the two press elements are joined; likewise, the wire bundles in their entirety are firmly pressed against the inner wall of the passage opening. This arrangement purports to prevent liquids and/or gases from passing between the individual wires and from passing between the outer circumference of the wire bundles and the inner surface of the bipartite device.
Thus, conventionally, water tightness or water blocking is achieved by providing a sealing compound or sheath around an individual wire or, in the case of a wire harness, around each individual wire and around the outer surface of the wire harness. Additionally, external pressure is exerted on the surface of the sheathed area of the wire or wire bundle such that no voids are left open between individual wires and between externally located wires and the surrounding sheath, the sheath preferably being a heat shrinkable hose which, under the influence of heat, tightly shrinks about an individual cable or a cable bundle at a desired position. The sheath acts as a moisture block where provided along with the outer shirking hose permanently exposing an inwardly directed force onto the sheath, thereby achieving the desired water tightness.
If a wire harness provided as described above is positioned, for example, in a partition between the engine compartment and th passenger compartment of a motor vehicle such that the treated portion of the wire harness is located within a hole provided in the partition, water migration is prevented. Specifically, water, and other fluids, that may enter the engine compartment and migrate on the insulation coating of individual wires or of the wires forming the wire harness, maynot migrate beyond the fluid blocking sealing compounds and maynot enter the passenger compartment. Thus, fluid maynot reach the non-insulated exposed ends of the wires which provide electric connection to various components.
The present invention provides an improved divided device for holding, guiding, and, leading elongated objects, for example, multiple wire bundles, there through. In particular, the present invention provides a grommet comprised of two half shells, each half shell being comprised of a press element and a connecting section element.
The grommet of the present invention comprises two interlocking half shells, each of which contains a press element and a connecting element. By interlocking the two half shells, elongated objects such as multiple wire bundles or the like may be retained in a desired position in a fluid-tight fashion. The grommet may be used for electrical wires, as well as for media-carrying conduits, whereby, the conduits may be guided, held, and led as well. Media-carrying conduits are, for instance, thin hollow bodies which carry liquids, e.g., washing liquids, cooling liquids or braking liquids, to their place of use.
The grommet is comprised of at lea,t one press element and at least one connecting section element that is linked to the press element in the direction of extension of the elongated objects. The sealing and dimensionally stable parting surfaces of the grommet allow it to replace ring-like or tubular soft rubber boots, which had been used previously in the art to hold or guide cable bundles and are produced by hand in a time-consuming manner.
In a preferred embodiment of the invention, the sealing and dimensional stability in the parting surfaces of the connecting section are ensured by the connection section consisting of an elastic material, such as EPDM or TPE, on its exterior, and a stiffening insert, such as PA, in its interior. Because of its structure, the connecting section is dimensionally stable so as to withstand external forces encountered during operation and allow no leakage in the area of the parting surfaces of the two connecting section parts, e.g., halves. The elastic material of the exterior of the connecting section also provides a fluid tight connection of the outer circumference of the grommet to the edge portion of wall openings, and is commonly found in sleeves or grommets, e.g., draw-in, press-in or push-in grommets.
A stiffening insert or xe2x80x9cskeletonxe2x80x9d located in the interior of at least the connecting section may also be provided consisting of an elastic flexible material. The stiffening insert or xe2x80x9cskeletonxe2x80x9d, consisting of a rigid, plastic material, such as PA, located in the interior of the connecting section of the bipartite grommet, is a precondition for the technically useful dividing and sealing functions of the grommet. The two halves of the grommet may be separated lengthwise and rejoined in a reliable and sealing manner. This contrasts with the prior art where separation of the halves would results in leaky areas on the parting surfaces upon the application of external forces.
The two half shells (or halves) are not in contact with one another at the time when a wire bundle is inserted. Following the insertion of the wire bundle, the two halves, which each comprise a press element surrounding the wire bundle and a connecting section element following the press element in longitudinal direction, are joined in the area of their parting planes. The parting planes are joined by screwing, locking, damping or in any other suitable manner. The wire bundle is fixed in the grommet according to the invention by exerting pressure on the wire bundle after the two halves have been joined. Possible methods for achieving the necessary pressure exertion include: (1) slightly over-dimensioning the wire bundle diameter relative to the fixed diameter of the passage channel formed between the joined press elements, (2) increasing the diameter of the wire bundle by sheathing the same with a suitable material; (3) inserting a rubber-like lining on the inner surfaces of the passage channel halves of the two press elements, thereby reducing the fixed diameter of the passage channel in pressure-exerting fashion; and (4) providing a flexible or semi-flexible, rubber-like material in the passage channel of the press elements, possibly provided for in only one of the two press elements of the grommet, with the material reducing the fixed diameter of the passage channel.
As to the sealing function of the grommet, a distinction should be made between xe2x80x9cwater tightness in the longitudinal directionxe2x80x9d and xe2x80x9cfluid-tight sealingxe2x80x9d. xe2x80x9cWater tightness in the longitudinal directionxe2x80x9d or longitudinal waterproof sealing, is meant to include liquids or gases being prevented from creeping through the grommet along the surfaces of the individual wires of the cable or wire bundle or along their insulating sleeves. Hence, within the scope of the present invention, xe2x80x9cwater tightness in the longitudinal directionxe2x80x9d designates the ability of the grommet to effectively prevent fluids from axially passing from one side of the grommet to the other side of the grommet. In contrast, within the scope of the present invention, the term xe2x80x9cfluid-tight sealingxe2x80x9d does not regard conditions prevailing inside the wire bundle, but conditions existing outside the wire bundle; in particular, sealing the outer circumference of the connecting section element so that the grommet may be secured in a wall opening.
In the grommet according to the invention, water tightness in the longitudinal direction may be achieved through the use of a butyl sealing compound, as described in DE 44 41 513 A1, or any other suitable sealing compound, e.g. a pressable gel, a grease, or a suitable sealing and adhesive compound. This sealing compound is provided between the individual wires of the wire bundle or between their insulating sleeves, on areas where pressure is exerted following the joining of the two grommet halves. A resulting constant pressure on the sealing compound is achieved with the invention, preferably by also doing one of the following alternatives: (1) providing a rubber-like lining on the press elements, at least in the area of their passage channels, or (2) providing a flexible or semi-flexible, rubber-like plastic material in the press elements, at least in the area of the passage channels, possibly provided for in only one of the two press elements of the grommet.
The diameter of a wire bundle will be increased when a sealing compound is positioned between the individual wires of the wire bundle or between the insulating sleeves of these individual wires. A wire bundle having such an overdimension may be fixed in a correct position in the press elements when one press element is provided with two guide tongues that cooperate with receiving grooves formed in the opposite press element. The tongue and groove configurations ensure that the two grommet halves are joined centrally.
The above-mentioned guide tongues serve not only to position and center an overdimensioned wire bundle, but also serve as xe2x80x98level indicatorsxe2x80x9d for ensuring that a sufficiently high pressure is exerted on the sealing compound. To this end, a wire bundle whose diameter is oversized because of the sealing compound contained in t he wire bundle is checked a s to whether the diameter of the wire bundle corresponds to the height of the upper edge of the guide tongues. In case the wire bundle diameter does not reach the upper edges of the guide tongues, the wire bundle diameter may be stuffed with fillers until the stuffed wire bundle diameter reaches the upper edges of the guide tongues.
It follows from the above discussion that the dividable grommet of the invention is fluid-tight in all of its parting surfaces and also in its connecting portions with a wall opening. According to a preferred embodiment, water tightness in the longitudinal direction may be achieved by using a sealing compound, possibly in the form of an adhesive tape. Furthermore, the area formed by the press elements may not only be straight, but also bent or curved, or of any other desired design.
The grommet according to the invention provides many economic advantages. As a result of its dividing function, the conventional time-consuming and cost-intensive hand threading operation may be dispensed with. This, in turn, creates conditions under which simple and complicated wire bundles, such as cable harnesses for cars, may be produced in an automatic manner. Furthermore, according to the invention, water tightness in the longitudinal direction need no longer be created in a separate operation. Moreover, the dividable grommet according to the invention may be repaired and maintained easily if and when faults are to be located. The two halves of the grommet may be easily separated from one another and the interior of the grommet maybe inspected. The grommet, which is divided according to the invention and which permits a subsequent opening operation makes it possible to introduce additional electrical wires at a later time, and also to remove an originally provided electrical wire without impairing the grommet as a whole, its fluid tightness or its water tightness in the longitudinal direction.
The lengthwise water-tight variant of the dividable grommet according to the invention may replace the non-dividable rubber sleeves or boots, together with heat shrinkable tube and sealing components consisting of hot-melt type adhesives and the like, which have so far been used for the purpose of achieving water tightness in the longitudinal direction. As a consequence, the expensive threading of wire bundles, i.e., through the use of conventional rubber sleeve and the conventional shrinkable tube, may be dispensed with.
The technical progress made with the present inventive method stems not only from being able to provide precise positioning and fixation for an elongated object, such as a wire bundle, but also from being able to guarantee that the two half shells of the grommet are connected in a fluid-tight and dimensionally stable, or torsionally rigid, manner. Advantageous developments of the invention permit the exertion of a constant pressure on the elongated object, e.g., wire bundle. The constant pressure being exerted on the elongated object may be provided in the following ways: (1) slightly over-dimensioning the elongated object, (2) stuffing the elongated object, (3) providing a rubber-like inner lining in the two press elements to be used, or (4) producing the press elements with a flexible or semiflexible, rubber-like plastic material in the area of the passage channel.
The method of the invention may also be implemented such that a sealing compound is introduced between the individual wires or the individual wire insulations of a wire bundle. When this sealing compound, preferably butyl rubber, is acted upon by the above-mentioned pressure, the wire bundle is sealingly protected against the passage of liquids or gases, with the effect being that liquids or gases maynot pass from one side of the bipartite grommet to the other side. The bipartite rubber grommet to be used in the method of the invention is dimensionally stable, i.e. torsionally rigid, at least in the area of its parting or connection surfaces. Furthermore, in a preferred embodiment of the method according to the invention, use is made of a diameter of the elongated object, e.g., wire bundle, to ensure a constant pressure. The biparte grommet is equipped with suitable level indicators, or guide tongues, useful for this purpose.